U.S. patent application number 13/352122 was filed with the patent office on 2012-09-06 for waking up a wireless power transmitter from beacon mode.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Kevin Douglas Lee, Zhen Ning Low.
Application Number | 20120223589 13/352122 |
Document ID | / |
Family ID | 46752879 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120223589 |
Kind Code |
A1 |
Low; Zhen Ning ; et
al. |
September 6, 2012 |
WAKING UP A WIRELESS POWER TRANSMITTER FROM BEACON MODE
Abstract
This disclosure provides systems, methods and apparatus for
waking a wireless power transmitter from beacon mode. In one aspect
a wireless power receiver apparatus is provided. The wireless power
receiver apparatus includes a receive circuit comprising a receive
coil. This receive circuit is coupled to a load. The receive
circuit is configured to wirelessly receive power from a
transmitter device at a first power level to power the load. The
wireless power receiver apparatus further includes an adjustment
circuit configured to be powered by using the wirelessly received
power. The adjustment circuit is further configured to adjust a
characteristic of the load using the wirelessly received power for
a period of time to cause a detectable change in an operating
characteristic of the transmitter device for the period of
time.
Inventors: |
Low; Zhen Ning; (San Diego,
CA) ; Lee; Kevin Douglas; (San Diego, CA) |
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
46752879 |
Appl. No.: |
13/352122 |
Filed: |
January 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61448127 |
Mar 1, 2011 |
|
|
|
Current U.S.
Class: |
307/104 |
Current CPC
Class: |
H02J 50/12 20160201;
H02J 50/20 20160201; H04B 5/0037 20130101; Y04S 20/20 20130101;
H02J 7/00045 20200101; H02J 7/025 20130101 |
Class at
Publication: |
307/104 |
International
Class: |
H02J 17/00 20060101
H02J017/00 |
Claims
1. A wireless power receiver apparatus, comprising: a receive
circuit comprising a receive coil, the receive circuit being
coupled to a load, the receive circuit being configured to
wirelessly receive power from a transmitter device at a first power
level to power the load; and an adjustment circuit configured to be
powered by using the wirelessly received power, the adjustment
circuit being further configured to adjust a characteristic of the
load using the wirelessly received power for a period of time to
cause a detectable change in an operating characteristic of the
transmitter device for the period of time.
2. The wireless power receiver apparatus of claim 1, wherein the
receive circuit is configured to wirelessly receive power from the
transmitter device at a second power level in response to the
change in the operating characteristic of the transmitter device,
the second power level being higher than the first power level.
3. The wireless power receiver apparatus of claim 1, wherein the
characteristic of the load comprises an impedance of the load.
4. The wireless power receiver apparatus of claim 3, wherein the
adjustment circuit is configured to lower the impedance of the
load.
5. The wireless power receiver apparatus of claim 1, wherein the
adjustment circuit further comprises a switch, wherein the
adjustment circuit is configured to adjust a characteristic of the
load by altering a position of the switch.
6. The wireless power receiver apparatus of claim 5, wherein the
switch comprises a transistor.
7. The wireless power receiver apparatus of claim 5, wherein the
adjustment circuit is configure to close the switch to cause a
short.
8. The wireless power receiver apparatus of claim 1, wherein the
first power level corresponds to a low power mode of the
transmitter device.
9. The wireless power receiver apparatus of claim 1, wherein the
detectable change in the operating characteristic of the
transmitter device comprises an increase in supply current to a
driver circuit.
10. The wireless power receiver apparatus of claim 9, wherein the
transmitter device is configured to wirelessly output power at the
second level when the increase in supply current is above a
threshold.
11. A method for waking a wireless power transmitter from a low
power mode, the method comprising: wirelessly receiving power from
a transmitter device at a first power level to power a load;
adjusting an operating characteristic of the load using the
wirelessly received power during a period of time to cause a
detectable change in an operating characteristic of the transmitter
device for the period of time.
12. The method of claim 11, further comprising wirelessly receiving
power from the transmitter device at a second power level in
response to the change in the operating characteristic of the
transmitter device, the second power level being higher than the
first power level.
13. The method of claim 11, wherein the characteristic of the load
comprises an impedance of the load.
14. The method of claim 13, wherein adjusting the operating
characteristic comprises lowering the impedance of the load.
15. The method of claim 11, wherein adjusting the operating
characteristic comprises altering a position of a switch.
16. The method of claim 15, wherein adjusting comprises closing the
switch to cause a short.
17. The method of claim 11, wherein the first power level
corresponds to a low power mode of the transmitter device.
18. The method of claim 11, wherein the detectable change in the
operating characteristic of the transmitter device comprises an
increase in supply current to a driver circuit.
19. The method of claim 18, wherein the transmitter device is
configured to wirelessly output power at the second level when the
increase in supply current is above a threshold.
20. A wireless power receiver apparatus, comprising: means for
wirelessly receiving power, the means for wirelessly receiving
power being coupled to a load, the means for wirelessly receiving
power being configured to wirelessly receive power from a means for
wirelessly transmitting power at a first power level to power the
load; and means for adjusting configured to be powered by using the
wirelessly received power, the means for adjusting being further
configured to adjust a characteristic of the load using the
wirelessly received power for a period of time to cause a
detectable change in an operating characteristic of the means for
wirelessly transmitting for the period of time.
21. The wireless power receiver apparatus of claim 20, wherein the
means for wirelessly receiving is configured to wirelessly receive
power from the means for wirelessly transmitting at a second power
level in response to the change in the operating characteristic of
the means for wirelessly transmitting, the second power level being
higher than the first power level.
22. The wireless power receiver apparatus of claim 20, wherein the
characteristic of the load comprises an impedance of the load.
23. The wireless power receiver apparatus of claim 22, wherein the
means for adjusting is configured to lower the impedance of the
load.
24. The wireless power receiver apparatus of claim 20, wherein the
means for adjusting further comprising a means for switching,
wherein the means for adjusting is configured to adjust a
characteristic of the load by altering a position of the means for
switching.
25. The wireless power receiver apparatus of claim 24, wherein the
means for switching comprises a transistor.
26. The wireless power receiver apparatus of claim 24, wherein the
means for adjusting is configure to close the means for switching
to cause a short.
27. The wireless power receiver apparatus of claim 20, wherein the
first power level corresponds to a low power mode of the means for
wirelessly transmitting.
28. The wireless power receiver apparatus of claim 20, wherein the
detectable change in the operating characteristic of the means for
wirelessly transmitting comprises an increase in supply current to
a driver circuit.
29. The wireless power receiver apparatus of claim 28, wherein the
means for wirelessly transmitting is configured to wirelessly
output power at the second level when the increase in supply
current is above a threshold.
30. The wireless power receiver apparatus of claim 20, wherein the
means for wirelessly receiving power comprises a receive circuit
comprising a receive coil.
31. The wireless power receiver apparatus of claim 20, wherein the
means for adjusting comprises an adjustment circuit.
32. wireless power receiver apparatus of claim 20, wherein the
means for wirelessly transmitting comprises a transmit circuit
comprising a transmit coil.
33. A wireless power transmitter apparatus, comprising: a transmit
circuit comprising a transmit coil, the transmit circuit being
configured to wirelessly transmit power at a first level so as to
charge or power a receiver device; and a transmit controller
circuit configured cause the transmit circuit to wirelessly
transmit power at a second level in response to a detected change
in an operating characteristic based on an action of the receiver
device, the second power level being higher than the first power
level.
34. The wireless power transmitter apparatus of claim 33, wherein
the first power level corresponds to a low power mode.
35. The wireless power transmitter apparatus of claim 33, further
comprising a driver circuit configured to drive the transmit coil
with a signal having a duty cycle of substantially twenty percent
or less.
36. The wireless power transmitter apparatus of claim 33, wherein
the transmit circuit further comprises a driver circuit, and
wherein the detected change in the operating characteristic
corresponds to an increase in a supply current level to the driver
circuit.
37. The wireless power transmitter apparatus of claim 36, wherein
the transmit controller circuit is configured to cause the transmit
circuit to wirelessly transmit power at the second power level if
the increase in the supply current level is above a threshold.
38. A method for waking from a low power mode, comprising:
wirelessly transmitting power a first power level for a determined
period of time so as to power or charge a receiver device;
detecting a change in an operating characteristic based on an
action of the receiver device; and wirelessly transmitting power at
a second power level in response to the detected change, the second
power level being higher than the first power level.
39. The method of claim 38, wherein the first power level
corresponds to a low power mode.
40. The method of claim 38, further comprising driving a transmit
coil for wirelessly transmitting power with a signal having a duty
cycle of substantially twenty percent or less.
41. The method of claim 38, further comprising detecting an
increase in a supply current level to a driver circuit.
42. The method of claim 41, wherein wirelessly transmitting power
at a second power level comprises wirelessly transmitting power at
the second power level if the increase in the supply current level
is above a threshold.
43. A wireless power transmitter apparatus, comprising: means for
wirelessly transmitting power being configured to wirelessly
transmit power at a first level for a determined period of time so
as to power or charge a means for wirelessly receiving power; and
means for controlling configured to cause the means for wirelessly
transmitting power to wirelessly transmit power at a second level
in response to a detected change in an operating characteristic
based on an action of the means for wirelessly receiving power, the
second power level being higher than the first power level.
44. The wireless power transmitter apparatus of claim 43, wherein
the first power level corresponds to a low power mode.
45. The wireless power transmitter apparatus of claim 43, further
comprising a means for driving configured to drive the means for
wirelessly transmitting power with a signal having a twenty cycle
of substantially ten percent or less.
46. The wireless power transmitter apparatus of claim 43, wherein
the means for wirelessly transmitting power further comprises a
means for driving, and wherein the detected change in the operating
characteristic corresponds to an increase in a supply current level
to the means for driving.
47. The wireless power transmitter apparatus of claim 47, wherein
the means for controlling is configured to cause the means for
wirelessly transmitting power to wirelessly transmit power at the
second power level if the increase in the supply current level is
above a threshold.
48. The wireless power transmitter apparatus of claim 43, wherein
the means for wirelessly transmitting power comprises a transmit
circuit comprising a transmit coil.
49. The wireless power transmitter apparatus of claim 43, wherein
the means for controlling comprises a transmit controller
circuit.
50. The wireless power transmitter apparatus of claim 43, wherein
the means for wirelessly receiving power comprises a receive
circuit comprising a receive coil.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/448,127
entitled "WAKING UP A WIRELESS POWER TRANSMITTER FROM BEACON MODE"
filed on Mar. 1, 2011, the disclosure of which is hereby
incorporated by reference in its entirety.
FIELD
[0002] The present invention relates generally to wireless power.
More specifically, the disclosure is directed to waking a wireless
power transmitter from a low power mode.
BACKGROUND
[0003] An increasing number and variety of electronic devices are
powered via rechargeable batteries. Such devices include mobile
phones, portable music players, laptop computers, tablet computers,
computer peripheral devices, communication devices (e.g., Bluetooth
devices), digital cameras, hearing aids, and the like. While
battery technology has improved, battery-powered electronic devices
increasingly require and consume greater amounts of power. As such,
these devices constantly require recharging. Rechargeable devices
are often charged via wired connections that require cables or
other similar connectors that are physically connected to a power
supply. Cables and similar connectors may sometimes be inconvenient
or cumbersome and have other drawbacks. Wireless charging systems
that are capable of transferring power in free space to be used to
charge rechargeable electronic devices may overcome some of the
deficiencies of wired charging solutions. As such, wireless
charging systems and methods that efficiently and safely transfer
power for charging rechargeable electronic devices are
desirable.
SUMMARY OF THE INVENTION
[0004] Various implementations of systems, methods and devices
within the scope of the appended claims each have several aspects,
no single one of which is solely responsible for the desirable
attributes described herein. Without limiting the scope of the
appended claims, some prominent features are described herein.
[0005] Details of one or more implementations of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Other features, aspects, and
advantages will become apparent from the description, the drawings,
and the claims. Note that the relative dimensions of the following
figures may not be drawn to scale.
[0006] One aspect of the disclosure provides a wireless power
receiver apparatus. The wireless power receiver apparatus includes
a receive circuit comprising a receive coil. The receive circuit is
coupled to a load. The receive circuit is configured to wirelessly
receive power from a transmitter device at a first power level to
power the load. The wireless power receiver apparatus further
includes an adjustment circuit configured to be powered by using
the wirelessly received power. The adjustment circuit is further
configured to adjust a characteristic of the load using the
wirelessly received power for a period of time to cause a
detectable change in an operating characteristic of the transmitter
device for the period of time.
[0007] Another aspect of the disclosure provides an implementation
of a method for waking a wireless power transmitter from a low
power mode. The method includes wirelessly receiving power from a
transmitter device at a first power level to power a load. The
method further includes adjusting an operating characteristic of
the load using the wirelessly received power during a period of
time to cause a detectable change in an operating characteristic of
the transmitter device for the period of time.
[0008] Yet another aspect of the disclosure provides a wireless
power receiver apparatus. The wireless power receiver apparatus
includes means for wirelessly receiving power. The means for
wirelessly receiving power is coupled to a load. The means for
wirelessly receiving power is configured to wirelessly receive
power from a means for wirelessly transmitting power at a first
power level to power the load. The wireless power receiver
apparatus further includes means for adjusting configured to be
powered by using the wirelessly received power. The means for
adjusting is further configured to adjust a characteristic of the
load using the wirelessly received power for a period of time to
cause a detectable change in an operating characteristic of the
means for wirelessly transmitting for the period of time.
[0009] Another aspect of the disclosure provides a wireless power
transmitter apparatus. The wireless power transmitter apparatus
includes a transmit circuit comprising a transmit coil. The
transmit circuit is configured to wirelessly transmit power at a
first level so as to charge or power a receiver device. The
wireless power transmitter apparatus further includes a transmit
controller circuit configured cause the transmit circuit to
wirelessly transmit power at a second level in response to a
detected change in an operating characteristic based on an action
of the receiver device. The second power level is higher than the
first power level.
[0010] Another aspect of the disclosure provides an implementation
of a method for waking from a low power mode. The method includes
wirelessly transmitting power a first power level for a determined
period of time so as to power or charge a receiver device. The
method further includes detecting a change in an operating
characteristic based on an action of the receiver device. The
method further includes wirelessly transmitting power at a second
power level in response to the detected change. The second power
level is higher than the first power level.
[0011] Another aspect of the disclosure provides a wireless power
transmitter apparatus. The wireless power transmitter apparatus
includes means for wirelessly transmitting power being configured
to wirelessly transmit power at a first level for a determined
period of time so as to power or charge a means for wirelessly
receiving power. The wireless power transmitter apparatus further
includes means for controlling configured cause the means for
wirelessly transmitting power to wirelessly transmit power at a
second level in response to a detected change in an operating
characteristic based on an action of the means for wirelessly
receiving power. The second power level is higher than the first
power level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a functional block diagram of an exemplary
wireless power transfer system, in accordance with exemplary
embodiments of the invention.
[0013] FIG. 2 is a functional block diagram of exemplary components
that may be used in the wireless power transfer system of FIG. 1,
in accordance with various exemplary embodiments of the
invention.
[0014] FIG. 3 is a schematic diagram of a portion of transmit
circuitry or receive circuitry of FIG. 2 including a transmit or
receive coil, in accordance with exemplary embodiments of the
invention.
[0015] FIG. 4 is a functional block diagram of a transmitter that
may be used in the wireless power transfer system of FIG. 1, in
accordance with exemplary embodiments of the invention.
[0016] FIG. 5 is a functional block diagram of a receiver that may
be used in the wireless power transfer system of FIG. 1, in
accordance with exemplary embodiments of the invention.
[0017] FIG. 6 is a schematic diagram of a portion of transmit
circuitry that may be used in the transmit circuitry of FIG. 4, in
accordance with exemplary embodiments of the invention.
[0018] FIGS. 7A, 7B, 7C, and 7D are simplified block diagrams
illustrating a beacon power mode for transmitting power between a
transmitter and a receiver, in accordance with exemplary
embodiments of the invention.
[0019] FIG. 8 is a schematic diagram of a simplified wireless
charging system to illustrate the effect of the load of a receiver
device on the impedance of a transmit coil.
[0020] FIG. 9 is a plot showing the supply current of the driver
circuit of the wireless power transmitter as a function of the load
presented to the driver circuit.
[0021] FIG. 10 is a schematic diagram of transmit circuitry as
shown in FIG. 6 along with a portion of an exemplary wireless power
receiver circuitry.
[0022] FIG. 11 is a flowchart of an exemplary method for waking a
wireless power transmitter from a low power beacon mode, in
accordance with exemplary embodiments of the invention.
[0023] FIG. 12 is a flowchart of an exemplary method for waking
from a low power beacon mode, in accordance with exemplary
embodiments of the invention.
[0024] FIG. 13 is a flowchart of another exemplary method for
waking a wireless power transmitter from a low power beacon mode,
in accordance with exemplary embodiments of the invention.
[0025] FIG. 14 is a flowchart of another exemplary method for
waking from a low power beacon mode, in accordance with exemplary
embodiments of the invention.
[0026] FIG. 15 is a functional block diagram of a wireless power
receiver, in accordance with an exemplary embodiment of the
invention.
[0027] FIG. 16 is a functional block diagram of a wireless power
transmitter, in accordance with an exemplary embodiment of the
invention.
[0028] The various features illustrated in the drawings may not be
drawn to scale. Accordingly, the dimensions of the various features
may be arbitrarily expanded or reduced for clarity. In addition,
some of the drawings may not depict all of the components of a
given system, method or device. Finally, like reference numerals
may be used to denote like features throughout the specification
and figures.
DETAILED DESCRIPTION
[0029] The detailed description set forth below in connection with
the appended drawings is intended as a description of exemplary
embodiments of the invention and is not intended to represent the
only embodiments in which the invention may be practiced. The term
"exemplary" used throughout this description means "serving as an
example, instance, or illustration," and should not necessarily be
construed as preferred or advantageous over other exemplary
embodiments. The detailed description includes specific details for
the purpose of providing a thorough understanding of the exemplary
embodiments of the invention. The exemplary embodiments of the
invention may be practiced without these specific details. In some
instances, well-known structures and devices are shown in block
diagram form in order to avoid obscuring the novelty of the
exemplary embodiments presented herein.
[0030] Wirelessly transferring power may refer to transferring any
form of energy associated with electric fields, magnetic fields,
electromagnetic fields, or otherwise from a transmitter to a
receiver without the use of physical electrical conductors (e.g.,
power may be transferred through free space). The power output into
a wireless field (e.g., a magnetic field) may be received, captured
by, or coupled by a "receiving coil" to achieve power transfer.
[0031] FIG. 1 is a functional block diagram of an exemplary
wireless power transfer system 100, in accordance with exemplary
embodiments of the invention. Input power 102 may be provided to a
transmitter 104 from a power source (not shown) for generating a
field 105 for providing energy transfer. A receiver 108 may couple
to the field 105 and generate output power 110 for storing or
consumption by a device (not shown) coupled to the output power
110. Both the transmitter 104 and the receiver 108 are separated by
a distance 112. In one exemplary embodiment, transmitter 104 and
receiver 108 are configured according to a mutual resonant
relationship. When the resonant frequency of receiver 108 and the
resonant frequency of transmitter 104 are substantially the same or
very close, transmission losses between the transmitter 104 and the
receiver 108 are minimal. As such, wireless power transfer may be
provided over larger distance in contrast to purely inductive
solutions that may require large coils that require coils to be
very close (e.g., mms). Resonant inductive coupling techniques may
thus allow for improved efficiency and power transfer over various
distances and with a variety of coil configurations.
[0032] The receiver 108 may receive power when the receiver 108 is
located in an energy field 105 produced by the transmitter 104. The
field 105 corresponds to a region where energy output by the
transmitter 104 may be captured by a receiver 108. In some cases,
the field 105 may correspond to the "near-field" of the transmitter
104 as will be further described below. The transmitter 104 may
include a transmit coil 114 for outputting an energy transmission.
The receiver 108 further includes a receive coil 118 for receiving
or capturing energy from the energy transmission. The near-field
may correspond to a region in which there are strong reactive
fields resulting from the currents and charges in the transmit coil
114 that minimally radiate power away from the transmit coil 114.
In some cases the near-field may correspond to a region that is
within about one wavelength (or a fraction thereof) of the transmit
coil 114. The transmit and receive coils 114 and 118 are sized
according to applications and devices to be associated therewith.
As described above, efficient energy transfer may occur by coupling
a large portion of the energy in a field 105 of the transmit coil
114 to a receive coil 118 rather than propagating most of the
energy in an electromagnetic wave to the far field. When positioned
within the field 105, a "coupling mode" may be developed between
the transmit coil 114 and the receive coil 118. The area around the
transmit and receive coils 114 and 118 where this coupling may
occur is referred to herein as a coupling-mode region.
[0033] FIG. 2 is a functional block diagram of exemplary components
that may be used in the wireless power transfer system 100 of FIG.
1, in accordance with various exemplary embodiments of the
invention. The transmitter 204 may include transmit circuitry 206
that may include an oscillator 222, a driver circuit 224, and a
filter and matching circuit 226. The oscillator 222 may be
configured to generate a signal at a desired frequency, such as
468.75 KHz, 6.78 MHz or 13.56 MHz, that may be adjusted in response
to a frequency control signal 223. The oscillator signal may be
provided to a driver circuit 224 configured to drive the transmit
coil 214 at, for example, a resonant frequency of the transmit coil
214. The driver circuit 224 may be a switching amplifier configured
to receive a square wave from the oscillator 222 and output a sine
wave. For example, the driver circuit 224 may be a class E
amplifier. A filter and matching circuit 226 may be also included
to filter out harmonics or other unwanted frequencies and match the
impedance of the transmitter 204 to the transmit coil 214.
[0034] The receiver 208 may include receive circuitry 210 that may
include a matching circuit 232 and a rectifier and switching
circuit 234 to generate a DC power output from an AC power input to
charge a battery 236 as shown in FIG. 2 or to power a device (not
shown) coupled to the receiver 108. The matching circuit 232 may be
included to match the impedance of the receive circuitry 210 to the
receive coil 218. The receiver 208 and transmitter 204 may
additionally communicate on a separate communication channel 219
(e.g., Bluetooth, zigbee, cellular, etc). The receiver 208 and
transmitter 204 may alternatively communicate via in-band signaling
using characteristics of the wireless field 205.
[0035] As described more fully below, receiver 208, that may
initially have a selectively disablable associated load (e.g.,
battery 236), may be configured to determine whether an amount of
power transmitted by transmitter 204 and receiver by receiver 208
is appropriate for charging a battery 236. Further, receiver 208
may be configured to enable a load (e.g., battery 236) upon
determining that the amount of power is appropriate. In some
embodiments, a receiver 208 may be configured to directly utilize
power received from a wireless power transfer field without
charging of a battery 236. For example, a communication device,
such as a near-field communication (NFC) or radio-frequency
identification device (RFID may be configured to receive power from
a wireless power transfer field and communicate by interacting with
the wireless power transfer field and/or utilize the received power
to communicate with a transmitter 204 or other devices.
[0036] FIG. 3 is a schematic diagram of a portion of transmit
circuitry 206 or receive circuitry 210 of FIG. 2 including a
transmit or receive coil 352, in accordance with exemplary
embodiments of the invention. As illustrated in FIG. 3, transmit or
receive circuitry 350 used in exemplary embodiments may include a
coil 352. The coil may also be referred to or be configured as a
"loop" antenna 352. The coil 352 may also be referred to herein or
be configured as a "magnetic" antenna or an induction coil. The
term "coil" is intended to refer to a component that may wirelessly
output or receive energy for coupling to another "coil." The coil
may also be referred to as an "antenna" of a type that is
configured to wirelessly output or receive power. The coil 352 may
be configured to include an air core or a physical core such as a
ferrite core (not shown). An air core coil 352 allows the placement
of other components within the core area. Air core coils may be
somewhat susceptible to detuning when certain types of extraneous
physical devices are placed in the vicinity of the core. However,
an air core may more readily enable placement of the receive coil
218 (FIG. 2) within a plane of the transmit coil 214 (FIG. 2) where
the coupled-mode region of the transmit coil 214 (FIG. 2) may be
more powerful.
[0037] As stated, efficient transfer of energy between the
transmitter 104 and receiver 108 may occur during matched or nearly
matched resonance between the transmitter 104 and the receiver 108.
However, even when resonance between the transmitter 104 and
receiver 108 are not matched, energy may be transferred, although
the efficiency may be affected. Transfer of energy occurs by
coupling energy from the field 105 of the transmitting coil to the
receiving coil residing in the neighborhood where this field 105 is
established rather than propagating the energy from the
transmitting coil into free space.
[0038] The resonant frequency of the loop or magnetic coils is
based on the inductance and capacitance. Inductance may be simply
the inductance created by the coil 352, whereas, capacitance may be
added to the coil's inductance to create a resonant structure at a
desired resonant frequency. As a non-limiting example, capacitor
352 and capacitor 354 may be added to the transmit or receive
circuitry 350 to create a resonant circuit that selects a signal
356 at a resonant frequency. Accordingly, for larger diameter
coils, the size of capacitance needed to sustain resonance may
decrease as the diameter or inductance of the loop increases.
Furthermore, as the diameter of the coil increases, the efficient
energy transfer area of the near-field may increase. Other resonant
circuits formed using other components are also possible. As
another non-limiting example, a capacitor may be placed in parallel
between the two terminals of the coil 350. For transmit coils, a
signal 358 with a frequency that substantially corresponds to the
resonant frequency of the coil 352 may be an input to the coil
352.
[0039] In one embodiment, the transmitter 104 may be configured to
output a time varying magnetic field with a frequency corresponding
to the resonant frequency of the transmit coil 114. When the
receiver is within the field 105, the time varying magnetic field
may induce a current in the receive coil 118. As described above,
if the receive coil 118 is configured to be resonant at the
frequency of the transmit coil 118, energy may be efficiently
transferred. The AC signal induced in the receive coil 118 may be
rectified as described above to produce a DC signal that may be
provided to charge or to power a load.
[0040] FIG. 4 is a functional block diagram of a transmitter 404
that may be used in the wireless power transfer system of FIG. 1,
in accordance with exemplary embodiments of the invention. The
transmitter 404 may include transmit circuitry 406 and a transmit
coil 414. The transmit coil 414 may be the coil 352 as shown in
FIG. 3. Transmit circuitry 406 may provide RF power to the transmit
coil 414 by providing an oscillating signal resulting in generation
of energy (e.g., magnetic flux) about the transmit coil 414.
Transmitter 404 may operate at any suitable frequency. By way of
example, transmitter 404 may operate at the 13.56 MHz ISM band.
[0041] Transmit circuitry 406 may include a fixed impedance
matching circuit 409 for matching the impedance of the transmit
circuitry 406 (e.g., 50 ohms) to the transmit coil 414 and a low
pass filter (LPF) 408 configured to reduce harmonic emissions to
levels to prevent self-jamming of devices coupled to receivers 108
(FIG. 1). Other exemplary embodiments may include different filter
topologies, including but not limited to, notch filters that
attenuate specific frequencies while passing others and may include
an adaptive impedance match, that may be varied based on measurable
transmit metrics, such as output power to the coil 414 or DC
current drawn by the driver circuit 424. Transmit circuitry 406
further includes a driver circuit 424 configured to drive an RF
signal as determined by an oscillator 423. The transmit circuitry
406 may be comprised of discrete devices or circuits, or
alternately, may be comprised of an integrated assembly. An
exemplary RF power output from transmit coil 414 may be on the
order of 2.5 Watts.
[0042] Transmit circuitry 406 may further include a controller 415
for selectively enabling the oscillator 423 during transmit phases
(or duty cycles) for specific receivers, for adjusting the
frequency or phase of the oscillator 423, and for adjusting the
output power level for implementing a communication protocol for
interacting with neighboring devices through their attached
receivers. It is noted that the controller 415 may also be referred
to herein as processor 415. Adjustment of oscillator phase and
related circuitry in the transmission path may allow for reduction
of out of band emissions, especially when transitioning from one
frequency to another.
[0043] The transmit circuitry 406 may further include a load
sensing circuit 416 for detecting the presence or absence of active
receivers in the vicinity of the near-field generated by transmit
coil 414. By way of example, a load sensing circuit 416 monitors
the current flowing to the driver circuit 424, that may be affected
by the presence or absence of active receivers in the vicinity of
the field generated by transmit coil 414 as will be further
described below. Detection of changes to the loading on the driver
circuit 424 are monitored by controller 415 for use in determining
whether to enable the oscillator 423 for transmitting energy and to
communicate with an active receiver. As described more fully below,
a current measured at the driver circuit 424 may be used to
determine whether an invalid device is positioned within a wireless
power transfer region of the transmitter 404.
[0044] The transmit coil 414 may be implemented with a Litz wire or
as an antenna strip with the thickness, width and metal type
selected to keep resistive losses low. In a one implementation, the
transmit coil 414 may generally be configured for association with
a larger structure such as a table, mat, lamp or other less
portable configuration. Accordingly, the transmit coil 414
generally may not need "turns" in order to be of a practical
dimension. An exemplary implementation of a transmit coil 414 may
be "electrically small" (i.e., fraction of the wavelength) and
tuned to resonate at lower usable frequencies by using capacitors
to define the resonant frequency.
[0045] The transmitter 404 may gather and track information about
the whereabouts and status of receiver devices that may be
associated with the transmitter 404. Thus, the transmit circuitry
406 may include a presence detector 480, an enclosed detector 460,
or a combination thereof, connected to the controller 415 (also
referred to as a processor herein). The controller 415 may adjust
an amount of power delivered by the driver circuit 424 in response
to presence signals from the presence detector 480 and the enclosed
detector 460. The transmitter 404 may receive power through a
number of power sources, such as, for example, an AC-DC converter
(not shown) to convert conventional AC power present in a building,
a DC-DC converter (not shown) to convert a conventional DC power
source to a voltage suitable for the transmitter 404, or directly
from a conventional DC power source (not shown).
[0046] As a non-limiting example, the presence detector 480 may be
a motion detector utilized to sense the initial presence of a
device to be charged that is inserted into the coverage area of the
transmitter 404. After detection, the transmitter 404 may be turned
on and the RF power received by the device may be used to toggle a
switch on the Rx device in a pre-determined manner, which in turn
results in changes to the driving point impedance of the
transmitter 404.
[0047] As another non-limiting example, the presence detector 480
may be a detector capable of detecting a human, for example, by
infrared detection, motion detection, or other suitable means. In
some exemplary embodiments, there may be regulations limiting the
amount of power that a transmit coil 414 may transmit at a specific
frequency. In some cases, these regulations are meant to protect
humans from electromagnetic radiation. However, there may be
environments where a transmit coil 414 is placed in areas not
occupied by humans, or occupied infrequently by humans, such as,
for example, garages, factory floors, shops, and the like. If these
environments are free from humans, it may be permissible to
increase the power output of the transmit coil 414 above the normal
power restrictions regulations. In other words, the controller 415
may adjust the power output of the transmit coil 414 to a
regulatory level or lower in response to human presence and adjust
the power output of the transmit coil 414 to a level above the
regulatory level when a human is outside a regulatory distance from
the electromagnetic field of the transmit coil 414.
[0048] As a non-limiting example, the enclosed detector 460 (may
also be referred to herein as an enclosed compartment detector or
an enclosed space detector) may be a device such as a sense switch
for determining when an enclosure is in a closed or open state.
When a transmitter is in an enclosure that is in an enclosed state,
a power level of the transmitter may be increased.
[0049] In exemplary embodiments, a method by which the transmitter
404 does not remain on indefinitely may be used. In this case, the
transmitter 404 may be programmed to shut off after a
user-determined amount of time. This feature prevents the
transmitter 404, notably the driver circuit 424, from running long
after the wireless devices in its perimeter are fully charged. This
event may be due to the failure of the circuit to detect the signal
sent from either the repeater or the receive coil that a device is
fully charged. To prevent the transmitter 404 from automatically
shutting down if another device is placed in its perimeter, the
transmitter 404 automatic shut off feature may be activated only
after a set period of lack of motion detected in its perimeter. The
user may be able to determine the inactivity time interval, and
change it as desired. As a non-limiting example, the time interval
may be longer than that needed to fully charge a specific type of
wireless device under the assumption of the device being initially
fully discharged.
[0050] FIG. 5 is a functional block diagram of a receiver 508 that
may be used in the wireless power transfer system of FIG. 1, in
accordance with exemplary embodiments of the invention. The
receiver 508 includes receive circuitry 510 that may include a
receive coil 518. Receiver 508 further couples to device 550 for
providing received power thereto. It should be noted that receiver
508 is illustrated as being external to device 550 but may be
integrated into device 550. Energy may be propagated wirelessly to
receive coil 518 and then coupled through the rest of the receive
circuitry 510 to device 550. By way of example, the charging device
may include devices such as mobile phones, portable music players,
laptop computers, tablet computers, computer peripheral devices,
communication devices (e.g., Bluetooth devices), digital cameras,
hearing aids (and other medical devices), and the like.
[0051] Receive coil 518 may be tuned to resonate at the same
frequency, or within a specified range of frequencies, as transmit
coil 414 (FIG. 4). Receive coil 518 may be similarly dimensioned
with transmit coil 414 or may be differently sized based upon the
dimensions of the associated device 550. By way of example, device
550 may be a portable electronic device having diametric or length
dimension smaller that the diameter of length of transmit coil 414.
In such an example, receive coil 518 may be implemented as a
multi-turn coil in order to reduce the capacitance value of a
tuning capacitor (not shown) and increase the receive coil's
impedance. By way of example, receive coil 518 may be placed around
the substantial circumference of device 550 in order to maximize
the coil diameter and reduce the number of loop turns (i.e.,
windings) of the receive coil 518 and the inter-winding
capacitance.
[0052] Receive circuitry 510 may provide an impedance match to the
receive coil 518. Receive circuitry 510 includes power conversion
circuitry 506 for converting a received RF energy source into
charging power for use by the device 550. Power conversion
circuitry 506 includes an RF-to-DC converter 520 and may also in
include a DC-to-DC converter 522. RF-to-DC converter 520 rectifies
the RF energy signal received at receive coil 518 into a
non-alternating power with an output voltage represented by
V.sub.rect. The DC-to-DC converter 522 (or other power regulator)
converts the rectified RF energy signal into an energy potential
(e.g., voltage) that is compatible with device 550 with an output
voltage and output current represented by V.sub.out and I.sub.out.
Various RF-to-DC converters are contemplated, including partial and
full rectifiers, regulators, bridges, doublers, as well as linear
and switching converters.
[0053] Receive circuitry 510 may further include switching
circuitry 512 for connecting receive coil 518 to the power
conversion circuitry 506 or alternatively for disconnecting the
power conversion circuitry 506. Disconnecting receive coil 518 from
power conversion circuitry 506 not only suspends charging of device
550, but also changes the "load" as "seen" by the transmitter 404
(FIG. 2).
[0054] As disclosed above, transmitter 404 includes load sensing
circuit 416 that may detect fluctuations in the bias current
provided to transmitter driver circuit 424. Accordingly,
transmitter 404 has a mechanism for determining when receivers are
present in the transmitter's near-field.
[0055] When multiple receivers 508 are present in a transmitter's
near-field, it may be desirable to time-multiplex the loading and
unloading of one or more receivers to enable other receivers to
more efficiently couple to the transmitter. A receiver 508 may also
be cloaked in order to eliminate coupling to other nearby receivers
or to reduce loading on nearby transmitters. This "unloading" of a
receiver is also known herein as a "cloaking." Furthermore, this
switching between unloading and loading controlled by receiver 508
and detected by transmitter 404 may provide a communication
mechanism from receiver 508 to transmitter 404 as is explained more
fully below. Additionally, a protocol may be associated with the
switching that enables the sending of a message from receiver 508
to transmitter 404. By way of example, a switching speed may be on
the order of 100 .mu.sec.
[0056] In an exemplary embodiment, communication between the
transmitter 404 and the receiver 508 refers to a device sensing and
charging control mechanism, rather than conventional two-way
communication (i.e., in band signaling using the coupling field).
In other words, the transmitter 404 may use on/off keying of the
transmitted signal to adjust whether energy is available in the
near-field. The receiver may interpret these changes in energy as a
message from the transmitter 404. From the receiver side, the
receiver 508 may use tuning and de-tuning of the receive coil 518
to adjust how much power is being accepted from the field. In some
cases, the tuning and de-tuning may be accomplished via the
switching circuitry 512. The transmitter 404 may detect this
difference in power used from the field and interpret these changes
as a message from the receiver 508. It is noted that other forms of
modulation of the transmit power and the load behavior may be
utilized.
[0057] Receive circuitry 510 may further include signaling detector
and beacon circuitry 514 used to identify received energy
fluctuations, that may correspond to informational signaling from
the transmitter to the receiver. Furthermore, signaling and beacon
circuitry 514 may also be used to detect the transmission of a
reduced RF signal energy (i.e., a beacon signal) and to rectify the
reduced RF signal energy into a nominal power for awakening either
un-powered or power-depleted circuits within receive circuitry 510
in order to configure receive circuitry 510 for wireless
charging.
[0058] Receive circuitry 510 further includes processor 516 for
coordinating the processes of receiver 508 described herein
including the control of switching circuitry 512 described herein.
Cloaking of receiver 508 may also occur upon the occurrence of
other events including detection of an external wired charging
source (e.g., wall/USB power) providing charging power to device
550. Processor 516, in addition to controlling the cloaking of the
receiver, may also monitor beacon circuitry 514 to determine a
beacon state and extract messages sent from the transmitter 404.
Processor 516 may also adjust the DC-to-DC converter 522 for
improved performance.
[0059] FIG. 6 is a schematic diagram of a portion of transmit
circuitry 600 that may be used in the transmit circuitry 406 of
FIG. 4. The transmit circuitry 600 may include a driver circuit 624
as described above in FIG. 4. As described above, the driver
circuit 624 may be a switching amplifier that may be configured to
receive a square wave and output a sine wave to be provided to the
transmit circuit 650. In some cases the driver circuit 624 may be
referred to as an amplifier circuit. The driver circuit 624 is
shown as a class E amplifier, however, any suitable driver circuit
624 may be used in accordance with embodiments of the invention.
The driver circuit 624 may be driven by an input signal 602 from an
oscillator 423 as shown in FIG. 4. The driver circuit 624 may also
be provided with a drive voltage V.sub.D that is configured to
control the maximum power that may be delivered through a transmit
circuit 650. To eliminate or reduce harmonics, the transmit
circuitry 600 may include a filter circuit 626. The filter circuit
626 may be a three pole (C 614, L 612, C 616) low pass filter
circuit 626.
[0060] The signal output by the filter circuit 626 may be provided
to a transmit circuit 650 comprising a coil 618. The transmit
circuit 650 may include a series resonant circuit having a
capacitance 620 and inductance (e.g., that may be due to the
inductance or capacitance of the coil) that may resonate at a
frequency of the filtered signal provided by the driver circuit
624. The load of the transmit circuit 650 may be represented by the
variable resistor 622. The load may be a function of a wireless
power receiver 508 that is positioned to receive power from the
transmit circuit 650.
[0061] As described above, power may be wasted if the transmitter
device is wirelessly transmitting power when no receivers are
present. Rather than having a manual switch for activating the
transmitter, the transmitter 404 may be configured to selectively
transmit power based on the presence of a wireless power receiver
508 while using minimal power when no receivers are present. FIGS.
7A, 7B, 7C, and 7D are simplified block diagrams illustrating a
beacon power mode for transmitting power between a transmitter 704
and a receiver 708, in accordance with exemplary embodiments of the
invention. FIG. 7A illustrates a transmitter 520 having a low power
"beacon" signal 705 when there are no receive devices in the beacon
coupling-mode region 710 (i.e., positioned close enough to be able
to adequate power from beacon signal). The beacon signal 705 may
be, as a non-limiting example, such as in the range of .about.10 to
.about.20 mW RF. This signal may be adequate to provide initial
power to a device to be charged when it is placed in the
coupling-mode region. In some embodiments, the low power beacon
signal may be output by altering the duty cycle of the input signal
602 as shown in FIG. 6. For example the duty cycle may be lowered
to 10%, for example, such that power is output for a small fraction
of the total duty cycle. The duty cycle may be set to a variety of
ranges such as, but not limited to substantially 5% to 30%.
[0062] FIG. 7B illustrates a receive device 708 placed within the
beacon coupling-mode region 710 of the transmitter 704 transmitting
the beacon signal 705. The transmitter 704 may detect that the
receiver 708 is receiving power. For example, the additional power
may be sensed by the load sensing circuit 416 (FIG. 4) of the
transmitter 704. As a result, the transmitter 704 may enter a high
power mode.
[0063] FIG. 7C illustrates the transmitter 704 generating a higher
power signal 705' resulting in a higher power coupling-mode region
710'. As long as the receive device 530 is accepting power and, the
transmitter may be able to detect the presence of the receiver 708
and will remain in the higher power state. While only one receive
device 708 is illustrated, multiple receive devices may be present
in the coupling-mode region 710. If there are multiple receive
devices they may share the amount of power transmitted by the
transmitter 704 based on how well each receiver 708 is coupled. For
example, the coupling efficiency may be different for each receiver
708 depending on where the device is placed within the
coupling-mode region 710.
[0064] FIG. 7D illustrates the transmitter 704 generating the
beacon signal 705 even when a receiver 708 is in the beacon
coupling-mode region 710. This state may occur when receive device
708 is shut off, or the device cloaks itself, perhaps because it
does not need any more power.
[0065] In some embodiments, a receiver and a transmitter may
communicate on a separate communication channel (e.g., Bluetooth,
zigbee, etc). With a separate communication channel, the
transmitter may determine when to switch between beacon mode and
high power mode, or create multiple power levels, based on the
number of receive devices in the coupling-mode region 510 and their
respective power requirements.
[0066] In order to conserve power, it is advantageous to minimize
the amount of power output by the beacon signal. However, in some
cases, the lower the power output level of the beacon signal, the
more difficult it may be to detect power consumption to wake the
transmitter from the low power beacon mode. Furthermore, it is also
advantageous to wake up from beacon mode as soon as possible once
the transmitter 704 detects the presence of a receiver 708 that
wishes to receive power. For example, a receiver 708 may not
initially have any source of power other than from the transmitter
704. If the receiver 708 is powered via a battery that has no
remaining charge, then the only source of power for the receiver
708 may be from the wireless power transmitter 704. In this case,
it is advantageous for the transmitter 704 operating in a low power
beacon mode to detect the presence of the receiver 708 as soon as
possible to supply adequate power to the receiver to perform
various functions and provide power to the battery. As such,
certain aspects of exemplary embodiments described herein are
directed to enabling a transmitter 704 to more easily detect the
presence of a receiver 708 while transmitting a beacon signal at
the lowest amount of power possible. In some embodiments, the
receiver 708 may have no other source of electric power other than
the transmitter 704 and may use the beacon signal to actively
signal the transmitter 704.
[0067] When a receiver 708 is positioned within the field output by
the transmitter 704 and is able to or enabled to receive power from
the transmitter 708, various transmitter operating characteristics
may be altered due to the power being coupled from the field the
transmitter is generating. FIG. 8 is a schematic diagram of a
simplified wireless charging system 800 to illustrate the effect of
the load of a receiver device 808 on the impedance of a transmit
coil 814. The transmitter 804 has an impedance Z.sub.tx when
"looking into" the transmit coil 814. The receiver 808 with a
receive coil 818 may be characterized as a portion of the load the
transmitter 804 is driving. The load may have an impedance that is
represented by the reactance X.sub.rx of the receiver 808 (i.e.,
the imaginary load) and a resistance R.sub.rx of the receiver 808
(i.e., the real load). The impedance Z.sub.tx of the transmit coil
814 due to the presence of a receiver actively coupling with the
output of the transmitter 708 may be determined by the following
impedance transformation shown in Equation 1.
Z tx = .omega. 2 M 12 2 R rx R rx 2 + ( .omega. M 22 + X rx ) 2 + j
( .omega. M 11 - .omega. 2 M 12 2 ( .omega. M 22 + X rx ) R rx 2 +
( .omega. M 22 + X rx ) 2 ) Equation 1 ##EQU00001##
[0068] Z.sub.tx=Impedance looking into the transmit coil 814,
[0069] .OMEGA.=Frequency in radians,
[0070] M.sub.11=Self inductance of the transmit coil 814,
[0071] M.sub.22=Self inductance of the receive coil 818,
[0072] M.sub.12=Mutual inductance between the transmit coil 814 and
the receive coil 818,
[0073] R.sub.rx=Real load of the receiver 808, and
[0074] X.sub.rx=Imaginary load of the receiver 808.
[0075] If both the transmit coil 814 and receive coil 818 are
series tuned (i.e., configured to resonate at a common frequency),
then the equation above may be simplified such that the impedance
Z.sub.tx of the transmitter 708 may be determined by the following
impedance transformation shown in Equation 2 as the self inductance
of each of the transmit coil 814 and the receive coil 818 along
with the reactive components generally cancel each other.
Z tx = .omega. 2 M 12 2 R rx Equation 2 ##EQU00002##
[0076] As can be seen from Equation 2, there is an inverse
relationship between the impedance Z.sub.tx and the real load
R.sub.rx of the receiver 808. As such, changes in the real load
R.sub.rx of the receiver 808 may cause a corresponding change in
impedance Z.sub.tx at the transmit coil 818. More specifically, any
decrease in the real load R.sub.rx of the receiver 508 results in
an increased impedance Z.sub.tx at the transmit coil 814. Any
increase in the impedance Z.sub.tx at the transmit coil 814 may
result in an increase in the supply current of a power amplifier
424 configured to drive the transmit coil 814 (as the supply
current of the power amplifier may change as a function of the load
it drives). This increase in current may be sensed to detect the
presence of a receiver. Sensing changes in supply current due to an
increase in impedance may provide an additional mechanism for
sensing a receiver 808.
[0077] FIG. 9 is a plot showing the supply current of the driver
circuit 424 of the wireless power transmitter 804 as a function of
the load presented to the driver circuit 424. As shown in FIG. 9,
increasing the load impedance presented to the driver circuit 424
creates a corresponding increase in the supply current of the
driver circuit 424. Using Equation 2 above, Equation 3 shows the
relationship regarding the change in the supply current of the
driver circuit 424 as the load at the receiver 808 decreases.
.dwnarw.R.sub.rx=.uparw.Z.sub.tx=.uparw.I.sub.PA Equation 3
[0078] If a receiver 808 can cause a significant increase in the
load impedance presented to the driver circuit 424, the resulting
increase in supply current to the driver circuit 424 may be more
significant. The higher the increase in the supply current of the
driver circuit 424, the easier it may be to detect the presence of
a receiver 808 at the transmitter 404 to trigger a change in
operating mode from the low power beacon mode. As such, if the
receiver 808 can cause a significant change in its real load
R.sub.rx, the corresponding impedance Z.sub.tx change may result in
a significant increase in the supply current of the driver circuit
424 for detecting the presence of the receiver 808.
[0079] FIG. 10 is a schematic diagram of transmit circuitry 1006 as
shown in FIG. 6 along with a portion of an exemplary wireless power
receiver circuitry 1010, in accordance with exemplary embodiments
of the invention. As in FIG. 6, the transmit circuitry 1006 may
have a switching amplifier 1024 driving a transmit circuit 1050
(including a transmit coil 1052) via a filter circuit 1026.
[0080] Receive circuitry 1010 may include a receive circuit 1060
including a receive coil 1062. The receive coil 1062 may couple
energy via a field 1005 output from the transmit coil 1052 as
described above. The receive circuitry 1010 may further include
rectifier circuitry 1080 configured to convert an AC signal
produced by the receive circuit 1060 into a DC signal that may be
used to charge a load R.sub.load. In some embodiments, the load
R.sub.load may include a battery (not shown) that may be charged
via the DC signal output from rectifier circuitry 1080.
[0081] An adjustment circuit 1070 may be electrically connected
between the receive circuit 1060 and the rectifier circuitry 1080.
The adjustment circuit 1070 may be configured to adjust a
characteristic of the load R.sub.rx of the receive circuitry 1010
for a period of time. Adjusting a characteristic of the load
R.sub.rx may be done to cause a detectable change in an operating
characteristic of a transmitter device 1004 to indicate its
presence. More specifically, when the receive circuitry 1010 is
positioned to be able to receive power from the field 1005 from a
low power beacon signal, the adjustment circuit 1070 may be
configured to operate so as to lower the real load R.sub.rx for a
period of time. Lowering the real load R.sub.rx may cause an
increase in the impedance Z.sub.tx looking into the transmit
circuitry 1006. An increase in Z.sub.tx may be sensed by detecting
an increase in supply current of a power driver circuit 1024 as
described above. Detecting the increase may allow a transmitter
1004 to detect the presence of a receiver 1008 and waken from a low
power mode to start delivering higher output power.
[0082] In one aspect, the adjustment circuit 1070 may be configured
to maximize the reduction in the real load R.sub.rx for a period of
time so as to produce a sharp increase in the impedance Z.sub.tx at
the transmit circuit 1050. This results in a greater increase in
the current of the driver circuit 1024 as shown in FIG. 9 that may
be easier to detect. By causing a more dramatic increase in
current, the power output in the low power beacon mode may be
minimized as detection of the receive circuitry 1010 may be easier
despite low output power. In one embodiment, a significant, but
short term drop in R.sub.rx may be accomplished by including a
selectively enabled short in the adjustment circuit 1070. The
adjustment circuit 1070 may include a switch 1072 such as a field
effect transistor (FET) or other switching component. The switch
1072 may be selectively controlled by a controller circuit 1074 to
temporarily short the switch 1072. The short may create a sharp
decrease in the real load R.sub.rx and corresponding sharp increase
in the impedance Z.sub.tx and resulting increase in the supply
current of the driver circuit 1024 to make it easier for the
transmitter 1004 to detect the presence of the receiver 1008. As
the short created by the adjustment circuit 1070 may consume large
amounts of power, the switch 1072 may be closed for only a short
period, just enough for the transmitter 1004 to be able to detect
the presence of a receiver 1008 and awaken from the low power
beacon mode. This provides a mechanism for the receive circuitry
1010 to actively adjust an operating characteristic to wake a
transmit circuitry 1006 from a low power beacon mode.
[0083] The adjustment circuit 1070 of FIG. 10 shows how reducing
the R.sub.rx may be accomplished by using a shorted switch 1072. A
variety of other methods and techniques may be used by the
adjustment circuit 1070 to adjust an operating characteristic
(e.g., reducing R.sub.rx in some way) for a short period of time
for signaling a wireless power transmitter to wake from a low power
beacon mode.
[0084] In some embodiments, the source of power for actively
adjusting the operating characteristic (e.g., real load R.sub.rx)
may be derived substantially or wholly from a low power beacon
signal output by a transmitter 1004. For example, a battery that
normally provides power to the receiver 1008 may have no remaining
charge and be unable to provide power to be able to signal the
transmitter 1004. In other embodiments, a receiver 1008 may receive
all power wirelessly. As such, the receiver 1008 may need a way to
signal its presence to the transmitter 1004 without relying on any
other power sources besides the low beacon signal. In one
embodiment, power received and rectified substantially from the low
power beacon may be used to power the controller 1074 to
selectively short the switch 1072 for a short period of time for
allowing the transmitter 1004 to detect a change and wake from the
low power beacon mode. In some embodiments, the controller 1074 may
be, or is part of, a processor 516 as shown in FIG. 5 that performs
a variety of functions for controlling the operation of the
receiver. Received power from the beacon signal may be used to
activate and power the processor 516 to selectively activate the
switch 1072 for a period of time to decrease R.sub.rx during an
initialization process performed by the receiver when initially
powered on.
[0085] In other embodiments, the controller 1074 for an adjustment
circuit 1070 may be independent of a processor 516 that more
generally controls operations of the receiver 1008. The controller
1074 may be able to receive power via a rectifier 1080 derived from
the low power beacon signal to selectively short the switch 1072.
For example, in some embodiments, a general processor 516 may
require more power than is delivered by a beacon signal. The
adjustment circuit 1070 and controller 1074 may be able to use the
power from the beacon signal to signal its presence to the
transmitter 1004 as described above. Once the transmitter 1004
begins outputting at a higher power level, the processor 516 may be
activated and the receiver 1008 may operate normally. As such, one
aspect of certain embodiments allows a receiver to effectively
signal its presence by using power wholly or substantially derived
from a low power beacon signal. Several benefits may be obtained,
particularly where the receiver 1008 may not initially have its own
power source. Furthermore, by sharply reducing its real load
R.sub.rx (e.g., via a temporary short) a transmitter 1004 may more
easily be able to detect the presence of the receiver 1008 to begin
outputting higher power levels. Easier detection may allow the
beacon signal to have a minimum strength while still being able to
easily detect the receiver 1008.
[0086] FIG. 11 is a flowchart of an exemplary method for waking a
wireless power transmitter 1004 from a low power beacon mode, in
accordance with exemplary embodiments of the invention. It should
be appreciated that while FIGS. 1-10 show various configurations
and/or components or portions of transmitters and receivers, any of
the components or portions shown may be included within any of the
functional receiver or transmitter blocks of any of FIGS. 1-10. For
example, a component shown in a transmitter of FIG. 4 may be
included in any of the transmitter blocks of FIGS. 6-10 and vice
versa. The method may begin in block 1102 when a receiver 1008 is
positioned to be able to receive a lower power beacon signal from a
transmitter 1004. As described above, the beacon signal may be
output at a low duty cycle (e.g., around 10%) to conserve power. In
block 1104, the receiver 1008 may use the received power to provide
power to a receiver processor that may begin to perform a
initialization process. As part of the initialization process, the
receiver 1008 may short a signaling switch 1072 that temporarily
reduces a real load R.sub.rx of the receiver 1008 as shown in block
1006. This may cause a corresponding change in the impedance
Z.sub.tx of the transmitter 1004 such that the transmitter 1004 is
able to detect the presence of the receiver 1008 and begin
delivering power at a higher level as compared to the power level
of the low power beacon signal. In block 1108, the receiver 1008
may complete the initialization process.
[0087] In block 1110, the receiver 1008 may open the signaling
switch 1072 to return the receiver 1008 to a normal operation mode.
The amount of time that the switch 1072 is shorted may be
configured to be just long enough to ensure that the transmitter
1004 is able to detect a change in the load of the driver circuit
1024 to be able to determine that a receiver 1008 is present. This
may allow the transmitter 1004 to wake up from beacon mode within
the shortest possible time while consuming minimum power to output
the beacon signal. Additionally, as the signaling switch 1072 burns
a significant amount of power while shorted, the signaling switch
1072 may be configured to only be shorted for a brief amount of
time to prevent damage to the receiver 1008. In block 1112, the
receiver 1008 may then signal to register with the transmitter
1004.
[0088] FIG. 12 is a flowchart of an exemplary method for waking
from a low power beacon mode, in accordance with exemplary
embodiments of the invention. In block 1202, a transmitter 1004 may
transmit low power beacon signals when a receiver 1008 is not
present to receive power. In decision block 1204, the transmitter
1004 may determine whether a change in current of a power supply
(e.g., to a driver circuit 1024) is above a threshold. A high
enough change in current may correspond to a receiver signaling its
presence as described above. If the increase in current is not
above the threshold, then the transmitter 1004 may resume
transmitting low power beacon signals. If the change in current is
above a threshold, then the transmitter 1004 may wake up from a low
power beacon mode and listen for a receiver 1008 on reverse link.
The receiver 1008 may send a signal to register with the
transmitter 1004 and the transmitter 1004 may determine whether the
receiver 1008 is able to receive power valid through some type of
authentication and/or verification process as shown in decision
block 1208. If the receiver 1008 is not permitted to receive power,
then the transmitter 1004 may resume transmitting low power beacon
signals. If the receiver 1008 is validated, then the transmitter
1004 may enter a higher power mode (as compared to the beacon mode)
and transmit power at a higher power level while the receiver 1008
is present.
[0089] In some embodiments, the transmitter 1004 may wait to start
transmitting higher power levels until communication has been
completed between the transmitter 1004 and receiver 1008 to
determine whether the receiver 1008 is permitted to receive power
as shown in FIG. 12. In other embodiments, once the transmitter
1004 detects a receiver 1008 is present, the transmitter 1004 may
immediately begin outputting power at increased power levels. Any
authentication and/or verification may happen once the receiver
starts receiving power at higher levels. This may be helpful in
cases where the receiver 1008 has no other current power source
than the low power beacon signals output from transmitter 1004.
This may allow the transmitter 1004 to lower the power output level
of the beacon signal to a level that is just high enough to allow
the receiver 1008 to actively signal its presence using power
derived substantially or wholly from the beacon signal. As
described by exemplary embodiments above, significantly reducing
the real load R.sub.rx through, for example, creating a temporary
short, may provide a mechanism requiring little power to quickly
awaken the transmitter 408.
[0090] FIG. 13 is a flowchart of another exemplary method for
waking a wireless power transmitter 1004 from a low power beacon
mode, in accordance with exemplary embodiments of the invention. In
block 1302, a receiver 1008 may wirelessly receive power from a
transmitter 1004 at first power level to power a load. The load may
include the various circuitry and components of the receiver 1008.
The wirelessly received power may be from a low power signal from a
transmitter operating in a low power mode. In block 1304, the
receiver 1008 may adjust an operating characteristic of the load
using the wirelessly received power during a period of time to
cause a detectable change in an operating characteristic of the
transmitter 1004 for the period of time. For example, as described
above, the receiver 1008 may short a portion of the receive
circuitry 1010 to reduce its real load R.sub.rx. This may cause a
detectable change in an amount of supply current, for example,
going to a driver circuit 1024 of the transmitter 1004. Detecting
the increase may awaken the transmitter 1004 from the low power
mode to transmit at higher power levels for use by the receiver to
power or charge the load.
[0091] FIG. 14 is a flowchart of another exemplary method for
waking from a low power beacon mode, in accordance with exemplary
embodiments of the invention. In block 1402, a transmitter 1004 may
wirelessly transmit power at a first power level, the power being
wirelessly received by an unpowered receiver device to activate an
adjustment circuit of the receiver device using the transmitted
power. The first power level may correspond to a low beacon power
signal as described above. In block 1404, the transmitter 1004 may
detect a change in an operating characteristic based on an action
of the adjustment circuit. For example, the transmitter 1004 may
detect a change in a current to a driver circuit 1024 in response
to the adjustment circuit 1070 causing a reduction in the real load
R.sub.rx of the receiver 1008. In block 1406, the transmitter 1004
may wirelessly transmit power at a second power level in response
to the detected change, the second power level being higher than
the first power level. The second power level may correspond to a
level of power transmitted after the transmitter 1004 wakens from
beacon mode that may be at a level that may adequately power or
charge the receiver 1008.
[0092] FIG. 15 is a functional block diagram of a wireless power
receiver 1500, in accordance with an exemplary embodiment of the
invention. Wireless power receiver 1500 comprises means 1502 and
1504 for the various actions discussed with respect to FIGS.
1-14.
[0093] FIG. 16 is a functional block diagram of a wireless power
transmitter 1600, in accordance with an exemplary embodiment of the
invention. Wireless power transmitter 1600 comprises means 1602,
1604 and 1606 for the various actions discussed with respect to
FIGS. 1-14.
[0094] The various operations of methods described above may be
performed by any suitable means capable of performing the
operations, such as various hardware and/or software component(s),
circuits, and/or module(s). Generally, any operations illustrated
in the Figures may be performed by corresponding functional means
capable of performing the operations.
[0095] Those of skill in the art would understand that information
and signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0096] Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the exemplary embodiments disclosed
herein may be implemented as electronic hardware, computer
software, or combinations of both. To clearly illustrate this
interchangeability of hardware and software, various illustrative
components, blocks, modules, circuits, and steps have been
described above generally in terms of their functionality. Whether
such functionality is implemented as hardware or software depends
upon the particular application and design constraints imposed on
the overall system. Skilled artisans may implement the described
functionality in varying ways for each particular application, but
such implementation decisions should not be interpreted as causing
a departure from the scope of the exemplary embodiments of the
invention.
[0097] The various illustrative logical blocks, modules, and
circuits described in connection with the exemplary embodiments
disclosed herein may be implemented or performed with a general
purpose processor, a Digital Signal Processor (DSP), an Application
Specific Integrated Circuit (ASIC), a Field Programmable Gate Array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0098] The steps of a method or algorithm described in connection
with the exemplary embodiments disclosed herein may be embodied
directly in hardware, in a software module executed by a processor,
or in a combination of the two. A software module may reside in
Random Access Memory (RAM), flash memory, Read Only Memory (ROM),
Electrically Programmable ROM (EPROM), Electrically Erasable
Programmable ROM (EEPROM), registers, hard disk, a removable disk,
a CD ROM, or any other form of storage medium known in the art. An
exemplary storage medium is coupled to the processor such that the
processor may read information from, and write information to, the
storage medium. In the alternative, the storage medium may be
integral to the processor. The processor and the storage medium may
reside in an ASIC. The ASIC may reside in a user terminal. In the
alternative, the processor and the storage medium may reside as
discrete components in a user terminal.
[0099] In one or more exemplary embodiments, the functions
described may be implemented in hardware, software, firmware, or
any combination thereof. If implemented in software, the functions
may be stored on or transmitted over as one or more instructions or
code on a computer readable medium. Computer readable media
includes both computer storage media and communication media
including any medium that facilitates transfer of a computer
program from one place to another. A storage media may be any
available media that may be accessed by a computer. By way of
example, and not limitation, such computer readable media may
comprise RAM, ROM, EEPROM, CD ROM or other optical disk storage,
magnetic disk storage or other magnetic storage devices, or any
other medium that may be used to carry or store desired program
code in the form of instructions or data structures and that may be
accessed by a computer. Also, any connection is properly termed a
computer readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of medium. Disk and disc,
as used herein, includes compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD), floppy disk and blu ray disc
where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above
should also be included within the scope of computer readable
media.
[0100] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database or another data
structure), ascertaining and the like. Also, "determining" may
include receiving (e.g., receiving information), accessing (e.g.,
accessing data in a memory) and the like. Also, "determining" may
include resolving, selecting, choosing, establishing and the
like.
[0101] The methods disclosed herein comprise one or more steps or
actions for achieving the described method. The method steps and/or
actions may be interchanged with one another without departing from
the scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
[0102] The previous description of the disclosed exemplary
embodiments is provided to enable any person skilled in the art to
make or use the present invention. Various modifications to these
exemplary embodiments will be readily apparent to those skilled in
the art, and the generic principles defined herein may be applied
to other embodiments without departing from the spirit or scope of
the invention. Thus, the present invention is not intended to be
limited to the exemplary embodiments shown herein but is to be
accorded the widest scope consistent with the principles and novel
features disclosed herein.
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